In the prior art of electronic transducers, either piezoelectric or magnetostrictive drivers are used as drivers for the desired ultrasonic vibration. The former have the advantage of high efficiency but the disadvantage of limited output power, due to the low tensile strength of piezoelectric materials. In contrast, higher output power can be generated with magnetostrictive ultrasonic transducers, but in this case the disadvantages of relatively lower efficiency, greater waste heat during operation and a more complex construction or a more expensive production method have to be taken into consideration.
One problem in the design of magnetostrictive ultrasonic transducers is that the magnetostrictive material must be joined appropriately to the ultrasonic horn, such a joint usually being produced in the prior art by means of a soldering method, especially a hard soldering method.
Generic magnetostrictive ultrasonic transducers of the aforesaid type are known, for example, from WO 2004/105085 A1 and WO 2006/055368 A2.
In these ultrasonic transducers, the driver consists of a large number of plates of magnetostrictive material (referred to hereinafter as magnet plates), which are fixed in recesses of the ultrasonic horn or to a surface of the ultrasonic horn by means of a hard soldering method. A suitable geometry of the magnet plates makes it possible to energize the plates with an alternating magnetic field. For this purpose the ultrasonic transducers described in the aforesaid publications are equipped, for example, with a central aperture in the magnet plates and a suitable coil arrangement, with which the two legs of the magnet plates bounding the aperture can be excited to vibrations in the ultrasonic frequency range by passing an appropriate current through the coil and in this way using the magnetostriction effect. These vibrations are then transmitted by the magnet plates to the ultrasonic horn and passed on inside the ultrasonic horn to its vibrating head. However, the disadvantages of magnetostrictive ultrasonic transducers already mentioned above also exist in this prior art.
Furthermore, from DD 59963 A there is known a method for joining electromechanical transducers with coupling elements and implements of ultrasonic generators, wherein the laminated core of a magnetostrictive transducer is joined to a plane end face of the ultrasonic generator by means of electron-beam welding in order to achieve coupling with the lowest possible loss. In this case high energy is needed for the electron beam, in order to weld the laminated core to the end face over the entire area thereof. In addition, this joining technique proves to be not particularly stable, since the laminated core is held exclusively against the plane face.
Finally, EP 0468125 A2 also discloses an ultrasonic horn in which two contiguous portions are joined to one another by means of electron-beam welding or laser-beam welding.